Variable capacity oil pump

ABSTRACT

A variable capacity oil pump controlling a pump discharge pressure to a two-stage characteristic includes: an electromagnetic switching valve formed to enable a switching between a state in which oil is discharged from a second control oil chamber and a state in which oil is introduced into the second control oil chamber; a pilot valve controlled by a discharge pressure by oil and a biasing force by a control spring and configured to supply a hydraulic pressure to a first control oil chamber in accordance with oil, to interrupt the supply of the hydraulic pressure, and to supply or exhaust the hydraulic pressure to or from second control oil chamber; and an intermediate passage. Oil exhausted from the first and second control oil chambers is not introduced into an inside of a control spring housing chamber in which a control spring of the pilot valve is arranged.

TECHNICAL FIELD

The present invention relates to a variable capacity oil pump which supplies oil which provides, for example, a lubrication of sliding locations of an internal combustion engine and a driving source of an auxiliary machinery of the internal combustion engine.

BACKGROUND ART

A conventional variable capacity oil pump is exemplified in a Patent Document 1 which will be described below. In the disclosed oil pump, a hydraulic pressure is supplied from a main gallery formed at a downstream side of a discharge passage to first and second control oil chambers or is exhausted via a drain passage. Thus, an eccentricity quantity with respect to a rotor of a cam ring is varied.

That is, the hydraulic pressure supplied from a first branch passage branched from the main oil gallery is introduced into an inside of the first control oil chamber so that the cam ring is moved in a direction in which the eccentricity quantity becomes small. On the other hand, the hydraulic pressure supplied from a second branch passage branched from the main oil gallery is introduced into the inside of the second control oil chamber caused so that the cam ring is moved in the direction in which the cam ring is moved in the direction in which the eccentricity becomes large.

Then, the introduction of the hydraulic pressure to the second control oil chamber is controlled in an on-and-off manner caused by a switching operation of an electromagnetic switching valve installed in the second branch passage. Thus, a pump discharge pressure is controlled in a two-stage characteristic between a low pressure and a high pressure.

In addition, a pilot valve which achieves a stability of the two-stage characteristic by adjusting an oil quantity of a working oil supplied into or exhausted from each of first and second control oil chambers is disposed in each of the above described branch passages.

This pilot valve includes a spool valve slidably housed at an inside of the corresponding pilot valve and controlled on a basis of a difference pressure between the hydraulic pressure supplied from the main gallery and a biasing force of a valve spring installed in the inside of the spool valve. Then, this pilot valve appropriately supplies or exhausts the hydraulic pressure into or from each of the first and second control oil chambers in accordance with its controlled positions. Then, when the hydraulic pressure is exhausted from each of these control oil chambers, each of the first and second control oil chambers and a pump external are communicated with each other via a spring housing chamber housing the valve spring and a drain port formed to be penetrated through a peripheral wall of the spring housing chamber.

However, since the conventional oil pump, as described hereinabove, is designed to exhaust the working oil within each of the first and second control oil chambers via the spring housing chamber of the pilot valve. In a case where the exhaust quantity is large and so forth, there is a possibility that, since the pressure within the spring housing chamber is raised and, accordingly, a variation in an internal pressure difference of the pilot valve occurs, a behavior of the spool valve becomes unstable and the pump discharge pressure cannot be controlled to a preset hydraulic pressure characteristic.

PRE-PUBLISHED DOCUMENT

Patent Document 1: a Japanese Patent Application Laid-open Publication No. 2014-105623.

DISCLOSURE OF THE INVENTION

With the above-described conventional technical task in mind, it is an object of the present invention to provide a variable capacity oil pump which is capable of improving a control accuracy of the pump discharge pressure with respect to the preset hydraulic pressure characteristic.

According to one aspect of the present invention, there is provided a variable capacity oil pump comprising: a pump constituting member which operatively discharges a working oil sucked from a suction section through a discharge section, with a volume of a plurality of pump chambers varied by a rotational drive through an internal combustion engine; a movable member which is operatively moved to modify a volume variation quantity of the plurality of pump chambers according to a movement of the movable member; a biasing mechanism which is installed in a state in which a set load is provided to bias the movable member in a direction in which the volume variation quantity of the plurality of pump chambers is increased; a first control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is decreased upon the movable member in response to a supply of the working oil into the first control oil chamber; a second control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is increased upon the movable member in response to a supply of the working oil into the second control oil chamber; a switching mechanism formed to enable a switching between a state in which the working oil from the second control oil chamber is exhausted and another state in which the working oil is introduced into the second control oil chamber; and a control mechanism configured to take a state in which the working oil within the first control oil chamber is exhausted and another state in which the working oil whose pressure is decreased than a discharge pressure from the discharge section is introduced into the first control oil chamber and to perform a pressure regulation for the working oil while applying the pressure to the working oil within the first control oil chamber by introducing the working oil into the first control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the state in which the working oil is exhausted from the second control oil chamber, and to take a further another state in which the working oil whose pressure is decreased than the discharge pressure from the discharge section is introduced into the second control oil chamber and a still further another state in which an introduction of the working oil into the second control oil chamber via the switching mechanism is interrupted and the working oil within the second control oil chamber is exhausted and to perform the pressure regulation for the working oil while reducing the pressure to the working oil within the second control oil chamber by exhausting the working oil within the second control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the other state in which the working oil is introduced into the second control oil chamber, wherein the control mechanism is controlled by a hydraulic pressure of the working oil and a biasing force of a biasing member and the working oil is not introduced into a location of the control mechanism at which the biasing member is arranged.

According to the present invention, the control accuracy of the pump discharge pressure with respect to the preset hydraulic pressure characteristic can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a rough configuration view representing an oil pump and a hydraulic pressure circuit of a variable capacity oil pump in a first preferred embodiment according to the present invention.

FIG. 2 is a front view representing a state in which a cover member of the variable capacity oil pump used in the first embodiment is removed.

FIG. 3 is a longitudinal cross sectional view of the variable capacity oil pump in the first embodiment.

FIG. 4 is a front view representing a pump body of the variable capacity oil pump in the first embodiment.

FIG. 5 is a longitudinal cross sectional view of an electromagnetic switching valve used in the first embodiment.

FIG. 6 is a longitudinal cross sectional view of a pilot valve used in the first embodiment according to the present invention.

FIG. 7 is an operation explanatory view of an electromagnetic switching valve in the first embodiment according to the present invention.

FIG. 8 is an operation explanatory view of the variable capacity oil pump in the first embodiment.

FIG. 9 is an operation explanatory view of the variable capacity oil pump in the first embodiment.

FIG. 10 is a graph representing a relationship between engine rotation numbers (speed) and a pump discharge pressure in the variable capacity oil pump in the first embodiment.

FIG. 11 is a longitudinal cross sectional view representing the pilot valve in a second preferred embodiment according to the present invention.

FIG. 12 is a longitudinal cross sectional view representing the pilot valve in a modification of the second embodiment.

EMBODIMENT FOR CARRYING OUT THE INVENTION

Hereinafter, each preferred embodiment of a variable capacity oil pump related to the present invention will be described in details on a basis of the accompanied drawings.

First Embodiment

FIG. 1 shows a variable capacity oil pump and its hydraulic circuit in a first preferred embodiment.

Variable capacity oil pump 10 is rotated by a rotational driving force transmitted from a crankshaft of an internal combustion engine, sucks oil which is a working oil reserved in an oil pan 01 from a suction passage 03 via a strainer 02, and, thereafter, discharges the working oil from a discharge passage 04 to a main oil gallery 05 formed within an inside of the engine.

A check ball type relief valve 07 which returns oil within oil pan 01 when a pump discharge pressure is excessively raised is disposed in a relief passage 06 branched from discharge passage 04.

In addition, an oil cooler (not shown) which serves to cool oil flowing through the oil cooler is disposed at a more downstream side than relief passage 06 of discharge passage 04 and a first oil filter 1 which collects a foreign matter within the flowing oil by means of a metallic mesh section (not shown).

Furthermore, a bypass passage 08 which bypasses first oil filter 1 is connected between an upstream side of first oil filter 1 and a downstream side of first oil filter 1 and located at a predetermined location of discharge passage 04 not passing through first oil filter 1 in discharge passage 04. A check ball type bypass valve 09 is disposed which is open to communicate the upstream side and the downstream side of bypass passage 08 when first oil filter 1, for example, clogs so that the oil flowing through first oil filter 1 becomes difficult.

The above-described main oil gallery 05 serves to supply oil to an oil jet which injects cooled oil to a slide section of the engine, for example, a piston, variably operated valve system (a valve timing control device), and bearings of a crankshaft of the engine. That is, oil passing through main oil gallery 05 is not only used as a lubricating oil lubricating a component provided in the inside of the engine but also used as a cooling purpose oil for a driving source of the variably operated valve system and which is injected through the oil jet.

A first branch passage 3 is branched in a midway through main oil gallery 05. This first branch passage 3 has an upstream section at which a second oil filter 2 is disposed and second and third branch passages 4, 5 are furthermore branched from a downstream side terminal section.

Second oil filter 2, as shown in FIG. 5, is constituted by a substantially cylindrical main body 2 a press fitted into an inner peripheral surface of first branch passage 3 and a metallic mesh section 2 b in a bottomed cylindrical shape coupled to one end section of main body 2 a in order to suppress particularly a flowing of contaminator mixed in oil into an electromagnetic switching valve 40 as will be described later.

In addition, each of first and second oil filters 1, 2 is of a cartridge type whose mesh section is detachably attached to a corresponding one of main bodies thereof and is replaceable in a case where a clogging occurs. It should be noted that each of first and second oil filters 1, 2 may serve to perform a filtering of oil through a replaceably attached filter paper.

Second branch passage 4 is communicable to first control oil chamber 31 of oil pump 10 via a pilot valve 50 which is a control mechanism as will be described later and a first supply/exhaust passage 7 a, as shown in FIG. 2. On the other hand, On the other hand, third branch passage 5 is communicable with a second control oil chamber 32 of oil pump 10 as will be described later via an electromagnetic switching valve 40 which is a switching mechanism electrically switching controlled, an intermediate passage 70, and pilot valve 50 and a second supply/exhaust passage 7 b.

Oil pump 10 is disposed at a front end section or so forth of a cylinder block 35 of the internal combustion engine. As shown in FIGS. 2 through 4, oil pump 10 includes: a housing having a pump body 11 in a cross sectional Japanese letter of a shape whose one end side formed to be open and having a pump housing chamber 13 and a cover member 12 which closes one end opening of pump body 11; a driving shaft 14 rotatably supported on the housing, penetrated through a substantial center section of pump housing chamber 13, rotatably supported on pump body 11 and cover member 12, and driven by means of a crankshaft of the engine; a rotor 15 rotatably housed within pump housing chamber 13 and whose center section is coupled to driving shaft 14; a plurality of vanes 16 housed movably in and out of a plurality of slits cut out radially on an outer peripheral section of rotor 15; a cam ring 17 which is a movable member and which partitions a space, together with rotor 15 and adjacent vanes 16, 16 into a plurality of pump chambers 20 and arranged on an outer peripheral side of each vane 16 to enable an eccentric swing (eccentrically movable) with respect to a rotation center of rotor 15; a cam spring 18 which is a biasing mechanism and which at any time biases cam ring 17 toward a direction toward which an eccentricity quantity with respect to rotor 15 (hereinafter, simply referred to as an eccentricity quantity) is increased; and a pair of ring members 19, 19 slidably arranged on both end sections of the inner peripheral side of rotor 15 and whose diameter is smaller than rotor 15.

It should be noted that driving wheel 14, rotor 15, and each vane 16 constitute a pump constituting member.

Pump body 11 is integrally formed by means of an aluminum alloy material. As shown in FIGS. 3 and 4, a bearing hole 11 a which rotatably supports one end section of driving axle 14 is penetrated through the substantial center position of a bottom surface 13 a of pump housing chamber 13. In addition, at a predetermined position of an inner peripheral wall of pump housing chamber 13 which provides an inner side surface of pump body 11, as shown in FIG. 4, a supporting hole 11 b into which a pivot pin 24 which is a swing fulcrum swingably supporting cam ring 17 is cut out. It should be noted that a retaining groove 11 e which serves as a lubrication of driving axle 14 is formed on the inner peripheral surface of bearing hole 11 a.

First and second seal sliding contact surfaces 11 c, 11 d on which two seal members 30, 30 as will be described later are respectively slidably contacted are formed at both sides of a straight line M (hereinafter called a cam ring reference line) connecting a center of bearing hole 11 a and a center of supporting hole 11 b, on an inner peripheral wall of pump housing chamber 13, as shown in FIG. 2. Seal members 30, 30 are disposed on an outer peripheral section of cam ring 17. These respective seal sliding contact surfaces 11 c, 11 d are formed in arcuate surface shapes and spaced apart from each other with predetermined radii R1, R2 from a center of supporting hole 11 b, as shown in FIG. 4.

In addition, on a bottom surface 13 a of pump housing chamber 13, as shown in FIGS. 2 and 4, a suction port 21 in a substantially arcuate recess shape which is a suction section and a drain port 22 in a substantially arcuate recess shape which is a discharge section are cut out on an outer peripheral area of bearing hole 11 a to substantially oppose against each other via bearing hole 11 a. Suction port 21 opens to a region (a suction region) whose inner volume of pump chamber 20 is increased in association with a pump action of the pump constituting member. Drain port 22 opens to a region (a discharge region) whose inner volume of pump chamber 20 is decreased in association with the pump action of the pump constituting member.

A suction hole 21 a in a substantially circular shape in cross sectional surface which opens externally and is penetrated through a bottom wall of pump body 11 is formed on a substantially center position of suction port 21. Thus, oil reserved in oil pan 01 of the engine is sucked into each pump chamber 20 of the suction region via suction passage 03, suction hole 21 a, and suction port 21.

It should be noted that suction hole 21 a is arranged and formed to a suction side outer peripheral area including a spring housing chamber 28 as will be described later of cam ring 17.

On the other hand, a discharge hole 22 a in a substantially circular shape in cross sectional surface which opens externally and is penetrated through the bottom wall of pump body 11 is formed at an upper position of drain port 22 in FIG. 4. Thus, oil within each pump chamber 20 of the discharge region whose pressure is applied to the pump action of the pump constituting member is supplied to main oil gallery 05 via drain port 22, discharge hole 22 a, and discharge passage 04 and, thus, is supplied to each slide section within the engine and the variably operated valve system.

Cover member 12 is formed in a substantially plate shape as shown in FIG. 3. A position of cover member 12 at an outer side section thereof which corresponds to bearing hole 11 a of pump body 11 is formed cylindrically (in a column shape).

Bearing hole 12 rotatably supporting the other end side of driving shaft 14 is penetrated through a substantial axial center position of this cylindrically shaped cover member 12. In addition, cover member 12 is attached onto an opening end surface of pump body 11 by a plurality of bolts 26.

Driving axle 14 is structured in order for rotor 15 to be rotated in a clockwise direction in FIG. 2 by a rotating force transmitted from a crankshaft (not shown) of the engine via a pulley or so forth.

The plurality of slits 15 a are cut out radially from an internal center side of rotor 15 toward a radial outside of rotor 15, as shown in FIG. 2. A plurality of back pressure chambers 15 b, each in a substantial circular shape in cross section, which introduce discharged oil into drain port 22 are formed at inside base end sections of respective slits 15 a.

Each vane 16 is pushed out externally by a centrifugal force involved in the rotation of rotor 15 and back pressures of back pressure chambers 15 b. Pump chambers 20 are defined in a liquid tight manner by an opposing inner side surface of adjacent vanes 16, 16, an inner peripheral surface of rotor 15, a bottom surface 13 a of pump housing chamber 13 of pump body 11, and an inner side surface of cover member 12.

An outer peripheral surface of each ring member 19 is slidably contacted on an inner end surface of base end section of each vane 16 and presses each vane 16 externally under pressure by the centrifugal force, as shown in FIGS. 2 and 3. Thus, even in a case where engine rotation numbers (an engine speed) is low and the back pressures within back pressure chambers 15 b are small, an outer end surface of a tip section of each vane 16 is brought in contact with the inner peripheral surface of cam ring 17 and a liquid tightness of each pump chamber 20 can be secured.

Cam ring 17 is integrally formed in an annular shape by a sintered metal. As shown in FIG. 2, a pivot section 17 a in a substantially arcuate recess shape is fitted into pivot pin 24 to constitute an eccentric swing fulcrum is projected at a predetermined position of the outer peripheral section of cam ring 17 along an axial direction of cam ring 17. In addition, an arm section 17 b which interlinks with cam spring 18 is projected along a radial direction of cam ring 17 opposite to pivot section 17 a with a center of cam ring 17 as a center.

A spring housing chamber 28 which is communicated with pump housing chamber 13 via a communication section 27 is disposed at a position of pump body 11 opposite to supporting hole 11 b. A tip section of arm section 17 b and cam spring 18 are housed within spring housing chamber 28.

One end section of cam spring 18 is elastically contacted on a substantially arc shaped supporting projection 17 c which is projected from a lower surface of the tip section of arm section 17 b and the other end of cam spring 18 is elastically contacted on the bottom surface of spring housing chamber 29.

A spring force (a biasing force) at any time biases cam ring 17 toward a direction at which the eccentricity quantity is increased (in a clockwise direction in FIG. 2) via arm section 17 b. Thus, cam ring 17, in an operation state shown in FIG. 2, an upper surface of arm section 17 b becomes a state in which an upper surface of arm section 17 b is pressed against a stopper surface 28 a formed on a lower surface of an upper wall of spring housing chamber 28 so as to be held at a position at which the eccentricity quantity becomes maximum.

In addition, a pair of first and second seal constituting sections 17 d, 17 e in a substantial triangular shape in cross section having first and second seal surfaces opposing against first and second seal sliding surfaces 11 c, 11 d are respectively projected on the other peripheral sections of the cam ring 17. First and second seal holding grooves in substantially arc recess shapes in cross section are cut out on respective seal surfaces along the axial direction of cam ring 17.

A pair of seal members 30, 30 are respectively housed and held which, during the eccentric swingable movement, slidably contacted on respective seal sliding contact surfaces 11 c, 11 d are housed and held at the insides of respective seal holding grooves.

As shown in FIG. 4, first and second seal surfaces are formed in arc surface shapes and spaced apart from each other with predetermined radii slightly smaller than radii R1, R2 from the center of supporting hole 11 b to each seal slide surfaces 11 c, 11 d are slidably contacted on respective seal sliding surfaces 11 c, 11 d with minute clearances.

Respective seal members 30, 30, as shown in FIG. 2, are formed in rectangular flat plate shapes, for example, with fluorine-containing resin materials having low friction characteristics along the axial direction of cam ring 17 and are pressed against respective seal sliding surfaces 11 c, 11 d by elastic forces exerted by rubber made elastic members disposed on bottom sections of the respective seal retaining grooves. Thus, the liquid tightness of each control oil chamber 31, 32 as will be described later is at any time secured.

Furthermore, first and second control oil chambers 31, 32 are respectively disposed with pivot section 17 a side of cam ring 17 as a center, namely, on an outer peripheral area of the pump discharge side.

These respective control oil chambers 31, 32 are defined so that an inner space in substantially arc shape in cross section defined by the inner peripheral surface of pump body 11, the outer peripheral surface of cam ring 17, and respective seal members 30, 30 is divided into two control oil chambers in a vertical direction of FIG. 2 by pivot section 17 a.

From among the first and second control oil chambers 31, 32, first control oil chamber 31 which is located at an upper side in FIG. 2 is connected to first supply/exhaust passage 7 a penetrated through a side section of pump body 11. The pump discharge pressure flowing within main oil gallery 05 is appropriately supplied to the first control oil chamber 31 via first and second branch passages 3, 4, pilot valve 50, and first communication hole 25 a.

In addition, a first pressure receiving surface 33 is formed which receives the hydraulic pressure supplied within first control oil chamber 31 is formed on the outer peripheral surface of cam ring 17 which faces toward first control oil chamber 31.

Thus, when the hydraulic pressure is supplied to first control oil chamber 31, a swing force in a direction against the biasing force of cam spring 18, viz., in a direction in which the eccentricity quantity is decreased is provided for cam ring 17.

On the other hand, second control oil chamber 32 is connected to second supply communication hole 25 b penetrated through the side section of pump body 11 in parallel to first communication hole 25 a. The pump discharge pressure flowing within main oil gallery 05 is appropriately supplied to second control oil chamber 32 via first and third branch passages 3, 5, electromagnetic switching valve 40, intermediate passage 70, pilot valve 50, and first communication hole 25 a.

A second pressure receiving surface 34 is formed on the outer peripheral surface of cam ring 17 which faces toward the second control oil chamber 32. Thus, when the hydraulic pressure is supplied within second control oil chamber 32, the swing force in the direction in which the eccentricity quantity is increased is provided in a direction in which the biasing force of cam spring 18 is assisted via second pressure receiving surface 34.

It should, herein, be noted that, as shown in FIG. 2, a pressure receiving area of first pressure receiving surface 33 is set to be larger than the pressure receiving area of second pressure receiving surface 34 and the biasing force based on the internal pressure of second control oil chamber 32 and the spring force of cam spring 18 are balanced with a predetermined force relationship.

It should, herein, be noted that electromagnetic switching valve 40 is, as described above, interposed between third branch passage 5 and intermediate passage 70 via which the hydraulic pressure is supplied to second control oil chamber 32.

Electromagnetic switching valve 40 is a two-port, three position valve, as shown in FIGS. 1, 2, and 5. Electromagnetic switching valve 40 serves to communicate third branch passage 5 with intermediate passage 70 or communicate third branch passage 70 with drain passage 6 on a basis of an ON or OFF signal transmitted in an engine driving condition from a control unit (not shown) controlling the engine.

That is, electromagnetic switching valve 40, as shown in FIG. 5, mainly includes: a valve body 41 press fitted into a valve housing hole 35 a fitted over a connection location between third branch passage 52 and intermediate passage 70 from an external of cylindrical block 35 and having an operation hole 41 a penetrated along an internal axial direction of the valve body; a valve seat 42 fitted into and fixed to a tip end side (one end section at an inside of cylinder block 35) of operation hole 41 a and having a center section on which a solenoid opening port 42 a communicated with a downstream end of third branch passage 5 is formed; a metallic ball valve body 43 disposed on an inside of a valve seat 42 to enable detachable seating; and a solenoid unit 44 coupled to a basic end section (other end section) of valve body 41.

Valve body 41 has a communication port 45 which is communicated with intermediate passage 70.

Communication port 45 is radially penetrated through valve body 41 at a side section of ball valve body 43 which is a tip end side of a peripheral wall of valve body 41. On the other hand, a drain port 46 which is communicated with drain passage (discharge passage) 6 is radially penetrated through a basic end section side of the peripheral wall of valve body 41.

Solenoid unit 44 has an inside in which an electromagnetic coil, a fixture plunger, a movable plunger, or so forth are housed. When a signal is issued from the control unit (not shown) to the electromagnetic coil, solenoid unit 44 accordingly moves the movable plunger forwardly or backwardly in the axial direction.

In addition, a return spring (not shown) to bias at any time the movable plunger in the backward direction is disposed in the inside of solenoid unit 44.

One end section of a cylindrical rod shaped push rod 47 is coupled to a tip section of the movable plunger. This push rod 47 is housed in operation hole 41 a. Ball valve body 43 can be pressed in the valve seat 42 direction via this push rod 47 under pressure.

In addition, a cylindrical passage 48 is formed between the outer peripheral surface of push rod 47 and the inner peripheral surface of a center section of operation hole 41 a. This cylindrical passage 48 is formed to appropriately communicate communication port 45 and drain port 46.

The above-described control unit detects the present engine driving condition from an oil temperature of the engine, a coolant temperature of the engine, engine rotation numbers (the engine rotation speed), a load of the engine, and so forth, outputs the ON signal (the power is supplied) to the electromagnet coil of solenoid unit 44 particularly when the engine rotation numbers (speed) is equal to or below a predetermined value, and outputs the OFF signal to the electromagnetic coil described above when the engine rotation numbers (the engine speed) is higher than the predetermined value and the engine load is in a high load region.

In the structure described above, for example, when the engine rotation numbers (engine speed) is equal to or below the predetermined value and, thus, the engine control unit outputs the ON signal (the power is supplied) to the electromagnetic coil of solenoid unit 44, the movable plunger is moved in the forward direction against the spring force of the return spring so that, as shown in a solid line of FIG. 5, ball valve body 43 is pressed toward the valve seat 42 direction via push rod 47 under pressure. Thus, ball valve seat 41 closes solenoid opening port 42 a and communicates the communication port 45, passage 48, and drain port 46. Hence, the hydraulic pressure within second control oil chamber 32 provides a state in which the hydraulic pressure within second control oil chamber 32 can be exhausted to oil pan 01 via pilot valve 50, communication port 401 via pilot valve 50, communication port 45, passage 48, and drain port 46.

On the other hand, for example, in a case where the engine rotation speed (numbers) is higher than the predetermined value, an OFF signal (non-power supply) is outputted from the control unit of the engine to the electromagnetic coil of solenoid unit 44. At this time, the movable plunger moves into the backward direction (retreats) by the spring force of the return spring. Thus, the pushing pressure (force) toward ball valve body 43. Thus, the pushing pressure toward ball valve body 43 by push rod 47 is released. At this time, the pump discharge pressure from third branch passage 5 is acted upon ball valve body 43 so that, as denoted by a dot-and-dash line of FIG. 5, ball valve body 43 is biased in the direction of solenoid unit 44. Thus, with one end of passage 48 closed, the communication between third branch passage 5 and intermediate passage 70 is communicated. Thus, the pump discharge pressure flowing through main oil gallery 05 can become supplied to second control oil chamber 32.

Hence, oil pump 10 is structured to select the supply or exhaust of the hydraulic pressure within second control of chamber 32 in association with the switching operation of electromagnetic switching valve 40 based on the driving state of the engine. Then, accordingly, oil pump 10 is structured to obtain two kinds of discharge pressure characteristics of a state in which the pump discharge pressure is controlled to a predetermined low pressure P1 by controlling the eccentricity quantity of cam ring 17 on a basis of the hydraulic pressure within first control oil chamber 31 supplied from main oil gallery 05 and the biasing force of cam spring 18 and another state in which the pump discharge pressure is controlled to a predetermined high pressure P2 by controlling the eccentricity quantity of cam ring 17 on a basis of the hydraulic pressure within first control oil chamber 31, the biasing force of cam spring 18, and the hydraulic pressure within second control oil chamber 32.

A setting load of cam spring 18 is set on a basis of the above-described two kinds of discharge pressure characteristics.

That is, for cam spring 18, the setting load is set in order to start operation when the hydraulic pressure of first control oil chamber 31 is equal to or above an operation start pressure P1′ lower than predetermined low pressure P1 in a case where the hydraulic pressure is supplied to only first control oil chamber 31 from among first and second control oil chambers 31, 32.

In addition, in a case where the same hydraulic pressure is supplied to each of first and second control oil chambers 31, 32, the force toward the direction against cam spring 18 is developed on a basis of a difference of the biasing force involved in a difference in area between both pressure receiving surfaces 33, 34. In this case, the setting load for cam spring 18 is set to start the operation when the hydraulic pressure supplied to both of first and second control oil chambers 31, 32 becomes equal to or above operation start pressure P2′ higher than predetermined high pressure P2.

It should be noted that, although there is a possibility that the hydraulic pressure when cam spring 18 starts to operate is varied in a case where the engine rotation numbers (the engine speed) is high, bubbles are included in the working oil, or so forth, the setting load is set for operation start pressure P2′ to be equal to or above desired high pressure P2 regardless of the engine driving condition.

Then, pilot valve 50 is disposed in oil pump 10.

As shown in FIGS. 2 and 6, pilot valve 50 includes: a cylindrically shaped valve body 51 integrally disposed against an outside wall of pump body 11; a spool valve 53 slidably housed in a sliding purpose hole 52 formed on an inside of valve body 51; a control spring 55 which is a basing member, housed within a control spring housing chamber 54 formed at the other end terminal in the axial direction of spool valve 53, and configured to bias spool valve in the upward direction in FIGS. 2 and 6; and a cup shaped press fit plug 56 press fitted and fixed to an opening of the other end section of valve body 51 in a state in which a spring load of control spring 55 is given. It should be noted that diameters of sliding purpose hole 52 and spool valve 53 (first and second land sections 63, 64 as will be described later) are set to be slightly larger than an outer diameter of control spring 53, with the outer diameter of control spring 53 as a reference.

An introduction port 57 whose diameter is smaller than sliding purpose hole 52 is formed on an upper end opening of sliding purpose hole 52 located at the upper direction in FIG. 6. This introduction port 57 is communicated with main oil gallery 05 via first and second branch passages 3, 4 and second oil filter 2.

In addition, a step difference tapered surface 51 a which is a seat surface on which spool valve 53 is biased in the upper direction by means of the spring force of control spring 55 and is seated is formed on an end edge of sliding purpose hole 52 of valve body 51 at the introduction port 57 side.

Furthermore, on a peripheral wall to which sliding purpose hole 52 of valve body 51 is exposed, a first supply/exhaust port 58 which is a first control port communicated with first control oil chamber 31 via first supply/exhaust passage 7 a, a second supply/exhaust port 59 which is a second control port communicated with second control oil chamber 32 via second supply/exhaust passage 7 b, and a drain port 60 located at an under side than second supply/exhaust port 59 and which is communicated with the atmospheric pressure outside of the pump are formed and penetrated along the radial direction.

In addition, a connection port 61 which is connected to one end of intermediate passage 70 and is radially penetrated on a part of the outer peripheral wall of valve body 51 which is located at an opposite direction to both of first and second supply/exhaust ports 58, 59 and which is parallel between first and second supply/exhaust ports 58, 59. In addition, a back pressure escaping purpose back pressure port 62 is radially penetrated thereon to secure a favorable sliding characteristic of spool valve 53 communicated with the atmospheric pressure at a position in a substantially circumferential direction with connection port 61 and at a lower side than drain port 60.

It should, herein, be noted that drain port 60 and back pressure port 62 can be communicated with suction port 21 not to the atmospheric pressure outside the pump.

Spool valve 53 is integrally formed in a solid manner and includes cylindrically shaped first and second land sections 63, 64 disposed respectively on both ends of spool valve 53 and whose diameters are comparatively large and a cylindrically shaped small diameter section 65 whose diameter is comparatively small and which connects both of first and second land sections 63, 64.

The outer diameters of first and second land sections 63, 64 are mutually the same. First and second land sections 63, 64 are slid on the inner peripheral surface of sliding purpose hole 52 with a minute clearance.

In addition, a distance between both of first and second land sections 63, 64 is set to satisfy a condition of the communication or interruption among respective ports 58 through 61 in first through fourth operation states of oil pump 10 as will be described later.

That is, a distance L1 between mutually opposing side surfaces 63 a, 64 a of first land section 63 and second land section 64 is set to be larger than an interval L2 between a lower end edge 58 a in FIG. 6 of first supply/exhaust port 58 and an upper end edge 59 a in FIG. 6 of second supply/exhaust port 59 and is set to be substantially equal to an interval L3 between lower end edge 61 a in FIG. 6 of connection port 61 and an upper end edge 60 a of drain port 60.

First land section 63 is set for an axial width of first land section 63 to be substantially equal to a hole diameter of first supply/exhaust port 58.

Furthermore, a cylindrically shaped pressure receiving section 66 whose diameter is slightly smaller than first land section 63 is projected on an end surface of first land section 63 at an introduction port 57 side. A flat surface shaped pressure receiving surface 66 a which receives the pump discharge pressure introduced into sliding purpose hole 52 from introduction purpose hole 52 from introduction port 57 is formed on a tip of pressure receiving section 66.

In addition, a small diameter cylindrically shaped convex section, viz., retaining projection section 67 whose diameter is smaller than second land section 64 is projected from an end surface of second land section 64 at a press fit plug 56 side.

Oil is circulated through small diameter section 65, as shown in FIGS. 2 and 6, via an annular ring shaped groove 68 formed on outer peripheries between small diameter section 65 and sliding purpose hole 52.

Control spring housing chamber 54 is cylindrically defined by an inner peripheral surface of sliding purpose hole 52, one end surface of spool valve 53 at press fit plug 56 side of second land section 64, and an inner end surface of press fit plug 56.

A spring force of control spring 55 is set to be smaller than the spring force of cam spring 18.

While one end section of control spring 55 is elastically contacted on the end surface of second land section 64 faced toward the press fit plug 56 side, the other end section of control spring 55 is elastically contacted on an inner end surface of press fit plug 56. This spring force at any time biases spool valve 53 toward introduction part 57 side.

Furthermore, control spring 55 is held by the outer peripheral surface of retaining projection section 67 and a substantially whole of the outer peripheral section of control spring 55 is held by the inner peripheral surface of control spring housing chamber 54.

Then, spool valve 53 is moved in the downward direction or in the upward direction according to a relative pressure on pressure receiving surface 66 a between the pump discharge pressure received from introduction port 57 and the spring force of control spring 55 so as to appropriately open or close (communicate) respective ports 57 through 61. The open or closure actions of respective ports 57 through 61 according to the operation of spool valve 53 will specifically be explained in an item of the following action in the first embodiment.

Action in the First Embodiment

Hereinafter, the operation of the variable capacity oil pump in the first embodiment will be explained on a basis of FIGS. 2 and 7 through 10.

First, in a case where the engine is started and in the driving state of a low rotation of the engine, oil pump 10 is in a first operation state shown in FIG. 2.

In this operation state, electromagnetic switching valve 40 is in a power supplied state upon receipt of the on signal in the internal electromagnetic coil from the control unit so as to push up ball valve body 43 in the direction of valve seat direction via the movable plunger and push rod 47 to close solenoid opening port 42 a and communication port 45 and drain port 46 are communicated with each other.

In addition, in pilot valve 50, the rotation numbers (speed) of the engine and the hydraulic pressure are low and the pump discharge pressure (a pilot pressure) acted upon pressure receiving surface 66 a is small, a state in which a tip end edge of pressure receiving surface 66 is seated on step-difference tapered surface 51 a is maintained without movement of spool valve 53 toward press fit plug 56 direction.

Thus, pilot valve 50 becomes a state in which first and second supply/exhaust ports 58, 59 are communicated with connection port 61 via ring shaped groove 68 located on the outer periphery of small diameter section 65.

Hence, in the first operation state, both of first control oil chamber 31 and second control oil chamber 32 are communicated with drain port 46. Thus, the eccentricity quantity control of cam ring 17 is carried out since without introduction of the hydraulic pressure into both of first and second control oil chambers 31, 31.

That is, cam ring 17 is maintained in a maximum eccentricity state in the clockwise direction in FIG. 2 by the spring force of cam spring 18, in other words, at a time when arm section 17 b is brought in contact with stopper surface 28 a not depending upon the hydraulic pressures within first and second control oil chambers 31, 32.

Consequently, in the first operation state, the pump discharge pressure of oil pump 10 is raised in a substantial proportion to the rise of rotation speed (numbers) of the engine, as shown in a rotation region a in FIG. 10.

Thereafter, when the rotation numbers of the engine (the engine speed) exceed rotation region a in FIG. 10 and, accordingly, the pump discharge pressure within main oil gallery 05 has reached to a low pressure P1 shown in FIG. 10, the state of oil pump 10 is transited to a second operation state shown in FIG. 7.

Even in this second operation state, the power supplied state of electromagnetic switching valve 40 is maintained in the same way as the first operation state.

In pilot valve 50, in the same way as first operation state, second control oil chamber 32 is communicated with drain port 46 by communicating second supply/exhaust port 59 with connection port 61 via ring shaped groove 68.

In addition, when the pump discharge pressure which is higher than low pressure P1 is received on pressure receiving surface 66 a of spool valve 53, pilot valve 50 is moved in the backward direction (retreated) against the spring force of control spring 55 so that introduction port 57 and first supply/exhaust port 58 are communicated with each other in an orifice state in which the opening area is throttled by means of first land section 63.

At this time, the hydraulic pressure supplied within first control oil chamber 31 indicates a pressure P1′ which is decreased than the pump discharge pressure due to the passage of this orifice section. However, since the set load of cam spring 18 is also set to be operated at operating start pressure P1′ in a case where the hydraulic pressure is supplied only to first control oil chamber from both of the first and second control oil chambers 31, 32. Thus, the control of pump discharge pressure can be carried out without influence of the pressure decrease by the orifice section.

Thus, the pressure decreased hydraulic pressure is supplied to first control oil chamber 31 via the orifice section which is expended in accordance with a height of the pump discharge pressure. The pump discharge quantity is decreased and the pump discharge quantity is reduced by biasing cam ring 17 in the direction in which the eccentricity quantity becomes small against the spring force of cam spring 53 on a basis of this supplied hydraulic pressure.

On the other hand, in pilot valve 50, in a case where the pump discharge pressure received by pressure receiving surface 66 a is lower than low pressure P1, spool valve 53 is moved in the introduction port 57 direction by the spring force of control spring 55. In the same way as the first operation state, first land section 63 serves to interrupt between introduction port 57 and first supply/exhaust port 58 and drain port 46 is communicated with first supply/exhaust port 58.

Thus, the hydraulic pressure within first control oil chamber 31 is decreased and the eccentricity (quantity) of cam ring 17 is accordingly increased so that the pump discharge quantity is increased and the pump discharge pressure is raised.

Hence, in the second operation state, while pilot valve 50 reduces the pump discharge pressure by pressure adjusting first control oil chamber 31 by introducing oil into first control oil chamber 31 as the pump discharge pressure of oil pump 10 becomes larger (higher), pilot valve 50 increases the pump discharge pressure by decreasing pressure by introducing oil from first control oil chamber 31 when the pump discharge pressure becomes low and, thus, pressure regulation to low pressure P1 is carried out.

It should be noted that, in the first embodiment, the hole diameter of first supply/exhaust port 58 and the axial width of first land section 63 which closes the first supply/exhaust port 58 are set to be substantially same length. Hence, the supply and exhaust of oil with respect to first control oil chamber 31 can switchably be controlled only through a minute movement of spool valve 53.

Thus, since an influence of a spring constant of control spring 55 on the discharge pressure control is slight, the pump discharge pressure can be controlled to low pressure P1 with a high accuracy.

Consequently, in the second operation state, the pump discharge pressure of oil pump 10 is maintained at low pressure P1 not relating to the rise in the engine rotation numbers (speed), as shown in a rotation region b of FIG. 10.

Next, when the load and the hydraulic pressure become high due to the further rise in the engine rotation numbers (speed) and the engine falls in the high load driving state in which the operation of the oil jet to inject oil toward the piston is required, oil pump 10 indicates a third operation state shown in FIG. 8.

In this third operation state, electromagnetic switching valve 40 becomes the non-power supply state when the internal electromagnetic coil of electromagnetic switching valve 40 receives the OFF signal from the control unit. Accordingly, the biasing of ball valve body 43 toward valve seat 42 direction is released. Hence, solenoid ball valve body 43 is biased toward solenoid unit 44 direction by the pump discharge pressure supplied via solenoid opening port 42 a. Hence, since one end of passage 48 is closed and the communication between communication port 45 and drain port 46 is interrupted.

Pilot valve 50 serves to communicate introduction port 57 with first supply/exhaust port 58 and to communicate second supply/exhaust port 59 with connection port 61. In addition, second land section 64 serves to interrupt between second supply/exhaust port 59 and drain port 60.

Hence, in the third operation state, the hydraulic pressure is introduced into both of first control oil chamber 31 and second control oil chamber 32. Hence, cam ring 17 is again moved in the clockwise direction in FIG. 8 by the spring force of cam spring 18 and the hydraulic pressure in second control oil chamber 32 and is again returned to the maximum eccentric state.

Consequently, in the third operation state, the pump discharge pressure of oil pump 10 is again raised in a substantially proportion to the rise in the engine rotation numbers (speed), as shown in a rotation region c of FIG. 10.

Thereafter, when the engine rotation numbers (speed) exceeds rotation region c and, accordingly, the discharge pressure of main oil gallery 05 reaches a high pressure P2 shown in FIG. 10, the state of oil pump is transited to a fourth operation state shown in FIG. 9.

Even in the fourth operation state, electromagnetic switching valve 40 is maintained in the non-power supplied state, in the same way as third operation state.

Pilot valve 50 serves to communicate introduction port 57 with first supply/exhaust port 58, in the same way as third operation state.

In addition, when pilot valve 50 receives the pump discharge pressure higher than high pressure P2 on pressure receiving surface 66 a, pilot valve 50 is moved in the backward direction (retreated) against the spring force of control spring 55 so that second supply/exhaust port 59 and drain port 60 are communicated to each other.

At this time, while the hydraulic pressure equal to the pump discharge pressure is supplied to first control oil chamber 31, the hydraulic pressure introduced in the third operation state is gradually exhausted from second control oil chamber 32 via drain port 60.

Thus, the force in the direction against cam spring 28 is not only a difference in the biasing force involved in an area difference between both of pressure receiving surfaces 33, 34 but receives the influence in the hydraulic pressure difference within both of first and second control chambers 31, 32, Consequently, the same state such that the pressure applied P2′ than the pump discharge pressure is supplied to both of first and second control oil chambers 31, 32.

Whereas, the setting load of cam spring 18 is set to be operated under operation start pressure P2′ in a case where the hydraulic pressure is supplied to both of first and second control oil chambers 31, 32. The control of the pump discharge pressure can be carried out without receiving the influence of the pressure decrease due to the exhaust of second control oil chamber 32.

Thus, second control oil chamber 32 is appropriately pressure decreased in accordance with a height of the pump discharge pressure. On a basis of the appropriate pressure decrease, cam ring 17 is moved in the direction in which the eccentricity quantity becomes small so that the pump discharge quantity is decreased and the pump discharge quantity is reduced.

On the other hand, in pilot valve 50, in a case where the pump discharge pressure under which pressure receiving surface 66 a receives becomes lower than high pressure P2, spool valve 53 moves in introduction port 57 direction by the spring force of control spring 56 and, in the same way as the third operation state, second supply/exhaust port 59 and drain port 60 are interrupted by second land section 64.

Thus, since the hydraulic pressure within second control oil chamber 32 is added (applied) and, accordingly, the eccentricity quantity of cam ring 17 is increased. Hence, when the pump discharge quantity is increased and the rise in the pump discharge pressure is achieved.

Hence, in the fourth operation state, while the pump discharge pressure is reduced by pressure decrease adjusting by a derivation of oil within second control oil chamber 32 as the pump discharge pressure of oil pump 10 becomes larger, the pressure applied adjusting by introducing oil into second control oil chamber 32 to increase the pump discharge pressure to perform a pressure regulation for the pump discharge pressure to high pressure P2.

It should, herein, be noted that, in this embodiment, since distance L1 between axially opposing side surfaces 63 a, 64 a of first and second land sections 63 and 64 is set to be substantially equal to an interval L3 of drain port 60 and connection port 61, the supply or exhaust of oil with respect to second control oil chamber 32 is switchably controlled only through a minute movement of spool valve 53. Thus, since the influence of the spring constant of control spring 55 is not easily given to the discharge pressure control, the pump discharge pressure can be controlled to high pressure P2 with a high accuracy.

Consequently, in the fourth operation state, the pump discharge pressure of oil pump 10 is substantially maintained at high pressure P2 without relation to the rise in the engine rotation numbers (speed).

In this way, in the first embodiment, the operation of pilot valve 50 is controlled via electromagnetic switching valve 40 so that the pump discharge pressure can be controlled to the two-stage characteristic of low pressure P1 and high pressure P2.

Then, in the first embodiment, pilot valve 50 is structured in order for oil to be circulated within control spring housing chamber 54 in all of first, second, third, and fourth operation states described before.

That is, in a case where oil is exhausted from first and second control oil chambers 31, 32 on a basis of the eccentricity quantity control of cam ring 17, this oil is exhausted to an external of oil pump 10 via ring shaped (annular) groove 68 formed at the center position of spool valve 53.

Because of this, in such a conventional technique that the hydraulic pressure of oil discharged from first and second control oil chambers 31, 32 is caused to flow into control oil spring housing chamber 54 and the back pressure within control oil spring housing chamber 54 occurs, such a problem that this back pressure causes the pump discharge pressure (pilot valve pressure) applied to pressure receiving surface 66 a and the position control of spool valve 53 by the spring force of control spring 55 to become unstable can be avoided.

Therefore, in the first embodiment, the control accuracy of the pump discharge pressure with respect to the set hydraulic pressure characteristic can be improved by improving a stability of the position control of spool valve 53. It should be noted that this effect is particularly effective in the fourth operation state in which a relatively high pressure oil is exhausted from second control oil chamber 32.

Incidentally, the bottomed cylindrical shaped spool valve having a pressure receiving wall on the one end section as in the conventional capacity oil pump is, in general, frequently used as the spool valve to be applied to pilot valve 50.

However, in such a bottomed cylindrically shaped spool valve as described above, a passage through which oil is circulated is needed on its peripheral wall. Hence, the shape thereof becomes complex.

In addition, since, in the inside of the bottomed cylindrically shaped spool valve, the one end side of control spring 55 is housed, a valve diameter larger than an outer diameter of control spring 55 is needed to be formed and, accordingly, the hole diameter of sliding purpose hole 52 is needed to become large in diameter to meet with the valve diameter. Thus, a large sizing of pilot valve 50 is resulted to be introduced.

Furthermore, since the outer diameter of control spring 55 with respect to hole diameter of control spring 55 becomes inevitably small, the other end side of control spring 55 becomes unstable state floating in the air. Thus, as a plug which seals sliding purpose hole 52, it is necessary to hold the other end side of control spring 55 using a screw plug having a groove section to hold the other end section of control spring 55 at an inside thereof. Consequently, there is a possibility that the large sizing of pilot valve 50 would be introduced.

In contrast, in the first embodiment, spool valve 53 is formed in the solid manner and the oil circulation is carried out via annular (ring shaped) groove 68 located on the outer periphery of small diameter section 65. Hence, the shape of spool valve 53 is relatively simple.

In addition, since control spring 55 is elastically contacted on the end surface of press fit plug 56 side of second land section 64, it becomes possible to set the valve diameter of spool valve 53 (the outer diameter of each of first and second land sections 63, 64) to be substantially equal to the outer diameter of control spring 55. Accordingly, the hole diameter of sliding purpose hole 52 can substantially be equal to or substantially be equal to the outer diameter of control spring 55. Consequently, the small sizing of pilot valve 50 can be achieved. In addition, since control spring 55 is guided on the outer peripheral surface of sliding purpose hole 52, the spring force of control spring 55 can be exhibited for the pump discharge pressure (pilot pressure) acted upon pressure receiving surface 66 a.

Furthermore, since control spring 55 is held by the inner peripheral surface of control spring housing chamber 54 (an inner peripheral wall of valve body 51), the sealing of sliding purpose hole 52 and the supporting of the other end section of control spring 55 can be carried out only by press fitting press fit plug 56 of a simple shape.

In addition, in the first embodiment, retaining projection section 67 is projected on one of the end surfaces of second land section 64 faced toward press fit plug 56 side. Since one end section of control spring 67 is grasped between the inner peripheral surface of valve body 51 and the outer peripheral surface of retaining projection section 67, a holding characteristic of control spring 55 is furthermore improved.

Furthermore, in the first embodiment, electromagnetic switching valve 40 is structured in such a way that, when oil is enabled to be exhausted from second control oil chamber 32, namely, in a case of the first operation state and the second operation state, electromagnetic switching valve 40 is in the non-power supply state and, when oil is enabled to be introduced into second control oil chamber 32, namely, in the case of the third and fourth operation states, electromagnetic switching valve 40 is in the non-power supplied state.

Thus, in a case, for example, the electromagnetic coil of electromagnetic switching valve 40 and a harness (not shown) are broken (line breakage), the high pressure characteristic is left even under a loss of the low pressure characteristic. Hence, the driving can be continued in a relatively safe manner.

Second Embodiment

FIG. 11 shows a second preferred embodiment according to the present invention. A basic structure of the second embodiment is the same as the first embodiment but a holding structure of control spring 55 of pilot valve 50 is modified.

A length of the axial width of second land section 64 of spool valve 53, in this embodiment, is longer than that in the first embodiment. In addition, in second land section 64, retaining projection section 67 is eliminated from the end surface of second land section 64 at control spring side 55 but, in this embodiment, a retaining groove section 71 which is a cylindrically shaped recess section is recessed at a substantial center position of the end surface of second land section 64 at control spring 55 side. A diameter of this retaining groove section 71 is smaller than the outer diameter of second land section 64 and is slightly larger than the outer diameter of control spring 55. A groove bottom of retaining groove section 71 is elastically contacted on one end section of control spring 55 and holds the one end section of control spring 55 by the peripheral wall of the retaining groove section 71.

In addition, press fit plug 56 is eliminated from the other end section side of control spring 55 of valve body 51 and a screw plug 72 which is a bottomed cylindrically shaped tubular member is screwed and fixed to the other end section side of control spring 55. An inner wall of a lid section 72 a of screw plug 72 is elastically contacted on the other end section of control spring 55 and an inner peripheral wall of a cylinder section 72 b holds the other end section of control spring 55.

Hence, also in this embodiment, in the same way as the first embodiment, oil exhausted from first and second control oil chambers 31, 32 is not circulated into control spring housing chamber 54. Hence, the stability of the position control of spool valve 53 can be improved and the control accuracy of the pump discharge pressure with respect to the set hydraulic pressure characteristic can be improved.

In addition, since both axial end sections of control spring 55 can be held in the stable state by the retaining groove section 71 of second land section 64 and the inner wall of screw plug 72, the spring force can accurately be exhibited against the pump discharge pressure (the pilot pressure) acted upon pressure receiving surface 66 a.

It should, herein, be noted that FIG. 12 shows a modification of the second preferred embodiment. Small diameter section 65 of spool valve 53 is formed to be made larger in diameter than that of the second preferred embodiment. In addition, retaining groove section 71 is recessed over an inside of small diameter groove section 71 from the end surface of second land section 64 at control spring 55 side. Hence, even in this case, the action and effect can be achieved in the same way as the second embodiment.

The present invention is not limited to the structures of the respective embodiments and various modifications and changes are made without departing from the gist of the present invention.

For example, in the second embodiment, a switching timing at which each port is switched by first and second land sections 63, 64 of spool valve 53 is simultaneous. However, such a state that both of drain port 60 and back pressure port 62 may simultaneously be communicated with each other or that both of drain port 60 and back pressure port 62 may be interrupted.

In addition, since chamfering or R shaping are carried out on axial both end edges of first and second sections 63, 64, characteristics of opening areas may be modified. These are adjusted to match with the characteristic of the engine.

In addition, in the second embodiment, with a fail-safe characteristic during the failure of electromagnetic switching valve 40 taken into consideration, the state of electromagnetic switching valve 40 enters the non-power supply state in a case of third and fourth operation states (engine high revolution state). However, it is possible to set reversely the power supply and the non-power supply.

Furthermore, a timing at which the power supply or non-power supply may appropriately be possible according to the various structures. For example, when the switching to the non-power supply state is carried out at a time point at which the engine rotation state becomes further high rotations. Oil pump 10 is directly switchable from the second operation state to the first operation state.

As the variable capacity oil pump based on the embodiment explained above, for example, the following aspects of the present invention may be considered.

In one aspect of the variable capacity oil pump, there is provided the variable capacity oil pump comprising: a pump constituting member which operatively discharges a working oil sucked from a suction section through a discharge section, with a volume of a plurality of pump chambers varied by a rotational drive through an internal combustion engine; a movable member which is operatively moved to modify a volume variation quantity of the plurality of pump chambers according to a movement of the movable member; a biasing mechanism which is installed in a state in which a set load is provided to bias the movable member in a direction in which the volume variation quantity of the plurality of pump chambers is increased; a first control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is decreased upon the movable member in response to a supply of the working oil into the first control oil chamber; a second control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is increased upon the movable member in response to a supply of the working oil into the second control oil chamber; a switching mechanism formed to enable a switching between a state in which the working oil from the second control oil chamber is exhausted and another state in which the working oil is introduced into the second control oil chamber; and a control mechanism configured to take a state in which the working oil within the first control oil chamber is exhausted and another state in which the working oil whose pressure is decreased than a discharge pressure from the discharge section is introduced into the first control oil chamber and to perform a pressure regulation for the working oil while applying the pressure to the working oil within the first control oil chamber by introducing the working oil into the first control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the state in which the working oil is exhausted from the second control oil chamber, and to take a further another state in which the working oil whose pressure is decreased than the discharge pressure from the discharge section is introduced into the second control oil chamber and a still further another state in which an introduction of the working oil into the second control oil chamber via the switching mechanism is interrupted and the working oil within the second control oil chamber is exhausted and to perform the pressure regulation for the working oil while reducing the pressure to the working oil within the second control oil chamber by exhausting the working oil within the second control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the other state in which the working oil is introduced into the second control oil chamber, wherein the control mechanism is controlled by a hydraulic pressure of the working oil and a biasing force of a biasing member and the working oil is not introduced into a location of the control mechanism at which the biasing member is arranged.

In a preferable aspect of the variable capacity oil pump, the control mechanism includes: a valve body having an introduction port through which the hydraulic pressure of the working oil discharged from the discharge section is introduced, a first control port communicated with the first control oil chamber, a second control port communicated with the second control oil chamber, and a drain port communicated with a connection port and a low pressure section connected to the switching mechanism; a spool valve slidably housed in an axial one end side of the valve body to switch between a communication state of the introduction port and the connection port with respect to the first control oil chamber and a communication state of the connection port and the drain port with respect to the second control oil chamber; and a control spring which is the biasing member and housed in the axial other end side of the valve body to blase the spool valve toward the axial one end of the valve body according to its biasing force smaller than that of the biasing mechanism.

According to another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, both axial end sections of the spool valve have the large-diameter land sections which slide the valve body and the small diameter sections are formed between respective land sections. The connection port is approximately communicated with respect to the first control oil chamber and is formed to appropriately communicated with the connection port and drain port with respect to the second control oil chamber.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the introduction port is installed at axial one end section of the valve body and pressure receiving surfaces on which the hydraulic pressure of working oil is acted are formed on axial end sections of the introduction port side.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the first and second control port and the drain port are penetrated through the peripheral wall of the valve body, respectively.

According to further another preferable aspect of the present invention, in any one of the aspects of the present invention, the spool valve is formed in the solid (body) manner.

According to further another preferable aspect of the present invention, in any one of the aspects of the present invention, the cylindrical recess section whose diameter is smaller than the land section is projected on the end surface of the land section at the control spring side and the convexity section is held by the convexity section.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the control spring is supported on the inner peripheral wall of the valve body.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the cylindrical recess section whose diameter is smaller than the land section is recessed toward the introduction port and one end side of the control spring is held by the recess section.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the bottomed cylindrically shaped tubular member is arranged on the valve body at the control spring side end section and the control spring other end section is held on the inner wall surface of the tubular member.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, in a case of the state in which the working oil is simultaneously exhausted from the first and second control oil chambers, the working oil is exhausted via the outer periphery of the small diameter section and, thereafter, via the switching mechanism.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the switching mechanism is an electromagnetically controlled valve electrically switching controlled.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the electromagnetically control valve takes a non-power supply state when the working oil is introduced into the second control oil chamber and takes the power supply state when the working oil is exhausted from the second control oil chamber.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the electromagnetically control valve carries out the switching of the working oil supply or exhaust with respect to the second control oil chamber through the ball valve.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the working oil discharged from the discharge section is used as the lubricating oil which lubricates the constituent member that the internal combustion engine has in its inside.

According to further another preferable aspect of the present invention, in any one of the aspects of the variable capacity oil pump, the working oil discharged from the discharge section is used in the oil jet which supplies the working oil to the piston of a drive source of the variably operated valve device and the piston of the internal combustion engine.

In addition, from another viewpoint, the variable capacity oil pump comprising: a rotor configured to be drivingly rotated by an internal combustion engine; a plurality of vanes movable out and into an outer peripheral section of the rotor; a cam ring configured to partition an inner peripheral side of the cam ring into a plurality of pump chambers while accommodating the rotor and the vanes into an inner peripheral side of the cam ring, to move to vary an eccentricity quantity with respect to an axial center of the rotor, and thereby to vary a volume variation quantity of the plurality of pump chambers; a suction section which is open to a suction region of the plurality of pump chambers in which a volume is increased in association with a rotation of the rotor; a discharge section which is open to a discharge region of the plurality of pump chambers in which the volume is decreased in association with the rotation of the rotor; a biasing mechanism disposed to have a set load and to bias the cam ring in a direction in which the eccentricity quantity becomes large; a first control oil chamber configured to act a force in a direction in which the eccentricity quantity becomes small upon the cam ring in response to a supply of the working oil into the first control oil chamber; a second control oil chamber configured to act a force in a direction in which the eccentricity quantity becomes large upon the cam ring in response to a supply of the working oil into the second control oil chamber; a switching mechanism formed to enable a switching between a state in which the working oil from the second control oil chamber is exhausted and a state in which the working oil is introduced into the second control oil chamber; and a control mechanism configured to take a state in which the working oil within the first control oil chamber is exhausted and another state in which the working oil whose pressure is decreased than a discharge pressure from the discharge section is introduced into the first control oil chamber and to perform a pressure regulation for the working oil while applying the pressure to the working oil within the first control oil chamber by introducing the working oil into the first control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the state in which the working oil is exhausted from the second control oil chamber, and to take a further another state in which the working oil whose pressure is decreased than the discharge pressure from the discharge section is introduced into the second control oil chamber and a still further another state in which an introduction of the working oil into the second control oil chamber via the switching mechanism is interrupted and the working oil within the second control oil chamber is exhausted and to perform the pressure regulation for the working oil while reducing the pressure to the working oil within the second control oil chamber by exhausting the working oil within the second control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the other state in which the working oil is introduced into the second control oil chamber, wherein the control mechanism is controlled by a hydraulic pressure of the working oil and a biasing force of a biasing member and the working oil is not introduced to into a location of the control mechanism at which the biasing member is arranged.

In a preferable aspect of the variable capacity oil pump, the first and second control oil chambers are installed on the outer peripheral side of the cam ring and are defined by the swing fulcrum disposed on the outer peripheral side of the cam ring. 

1. A variable capacity oil pump comprising: a pump constituting member which operatively discharges a working oil sucked from a suction section through a discharge section, with a volume of a plurality of pump chambers varied by a rotational drive through an internal combustion engine; a movable member which is operatively moved to modify a volume variation quantity of the plurality of pump chambers according to a movement of the movable member; a biasing mechanism which is installed in a state in which a set load is provided to bias the movable member in a direction in which the volume variation quantity of the plurality of pump chambers is increased; a first control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is decreased upon the movable member in response to a supply of the working oil into the first control oil chamber; a second control oil chamber configured to act a force in a direction in which the volume variation quantity of the plurality of pump chambers is increased upon the movable member in response to a supply of the working oil into the second control oil chamber; a switching mechanism formed to enable a switching between a state in which the working oil from the second control oil chamber is exhausted and another state in which the working oil is introduced into the second control oil chamber; and a control mechanism configured to take a state in which the working oil within the first control oil chamber is exhausted and another state in which the working oil whose pressure is decreased than a discharge pressure from the discharge section is introduced into the first control oil chamber and to perform a pressure regulation for the working oil while applying the pressure to the working oil within the first control oil chamber by introducing the working oil into the first control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the state in which the working oil is exhausted from the second control oil chamber, and to take a further another state in which the working oil whose pressure is decreased than the discharge pressure from the discharge section is introduced into the second control oil chamber and a still further another state in which an introduction of the working oil into the second control oil chamber via the switching mechanism is interrupted and the working oil within the second control oil chamber is exhausted and to perform the pressure so regulation for the working oil while reducing the pressure to the working oil within the second control oil chamber by exhausting the working oil within the second control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the other state in which the working oil is introduced into the second control oil chamber, wherein the control mechanism is controlled by a hydraulic pressure of the working oil and a biasing force of a biasing member and the working oil is not introduced into a location of the control mechanism at which the biasing member is arranged.
 2. The variable capacity oil pump as claimed in claim 1, wherein the control mechanism includes: a valve body having an introduction port through which the hydraulic pressure of the working oil discharged from the discharge section is introduced, a first control port communicated with the first control oil chamber, a second control port communicated with the second control oil chamber, and a drain port communicated with a connection port and a low pressure section connected to the switching mechanism; a spool valve slidably housed in an axial one end side of the valve body to switch between a communication state of the introduction port and the connection port with respect to the first control oil chamber and a communication state of the connection port and the drain port with respect to the second control oil chamber; and a control spring which is the biasing member and housed in the axial other end side of the valve body to blase the spool valve toward the axial one end of the valve body according to its biasing force smaller than that of the biasing mechanism.
 3. The variable capacity oil pump as claimed in claim 2, wherein the spool valve includes large-diameter land sections which slide together with the valve body and disposed at both axial ends of the spool valve and a small diameter section is formed between each of the land sections and the connection port is appropriately communicated with the first control oil chamber and the connection port and the drain port are appropriately communicated with the second control oil chamber, via an outer periphery of the small diameter section.
 4. The variable capacity oil pump as claimed in claim 3, wherein the introduction port is disposed on the axial one end of the valve body and a pressure receiving surface upon which the hydraulic pressure of the working oil is acted is formed on the spool valve at an axial end section of the introduction port side of the spool valve.
 5. The variable capacity oil pump as claimed in claim 4, wherein the first control port, the second control port, and the drain port are formed in a peripheral wall of the valve body to be penetrated through the peripheral wall of the valve body.
 6. The variable capacity oil pump as claimed in claim 5, wherein the spool valve is formed in a solid manner.
 7. The variable capacity oil pump as claimed in claim 5, wherein a cylindrical convex section whose diameter is smaller than each of the land sections is projected at an end surface side of each of the land sections at the control spring side thereof and the one end side of the control spring is held by the convex section.
 8. The variable capacity oil pump as claimed in claim 7, wherein the control spring is supported on an inner peripheral wall of the valve body.
 9. The variable capacity oil pump as claimed in claim 5, wherein a cylindrical recess section whose diameter is smaller than each of the land sections is recessed toward the introduction port side at one end surface of each of the land sections and the one end side of the control spring is held by the recess section.
 10. The variable capacity oil pump as claimed in claim 5, wherein a tubular member in a bottomed cylindrical shape is arranged at an end section of the valve body at the control spring side thereon and the other end side of the control spring is held on the inner peripheral surface of the tubular member.
 11. The variable capacity oil pump as claimed in claim 3, wherein, in a case of a state in which the working oil is simultaneously exhausted from the first and second control oil chambers, the working oil is exhausted via the switching mechanism after passing through an outer periphery of the small diameter section.
 12. The variable capacity oil pump as claimed in claim 1, wherein the switching mechanism is an electrically switching controlled electromagnetic control valve.
 13. The variable capacity oil pump as claimed in claim 12, wherein the electromagnetic control valve takes a non-power receiving state when the working oil is introduced into the second control oil chamber and takes a power receiving state when the working oil is exhausted from the second control oil chamber.
 14. The variable capacity oil pump as claimed in claim 13, wherein the electromagnetic control valve carries out the switching between the supply and the exhaust of the working oil with respect to the second control oil chamber through a ball valve.
 15. The variable capacity oil pump as claimed in claim 1, wherein the working oil discharged from the discharge section is used in a form of a lubricating oil which lubricates a constituting member that the internal combustion engine internally has.
 16. The variable capacity oil pump as claimed in claim 1, wherein the working oil discharged from the discharge section is used for an oil jet from which the working oil is supplied to a driving source of a variably operated valve system and a piston of the internal combustion engine.
 17. A variable capacity oil pump comprising: a rotor configured to be drivingly rotated by an internal combustion engine; a plurality of vanes movable out and into an outer peripheral section of the rotor; a cam ring configured to partition an inner peripheral side of the cam ring into a plurality of pump chambers while accommodating the rotor and the vanes into an inner peripheral side of the cam ring, to move to vary an eccentricity quantity with respect to an axial center of the rotor, and thereby to vary a volume variation quantity of the plurality of pump chambers; a suction section which is open to a suction region of the plurality of pump chambers in which a volume is increased in association with a rotation of the rotor; a discharge section which is open to a discharge region of the plurality of pump chambers in which the volume is decreased in association with the rotation of the rotor; a biasing mechanism disposed to have a set load and to bias the cam ring in a direction in which the eccentricity quantity becomes large; a first control oil chamber configured to act a force in a direction in which the eccentricity quantity becomes small upon the cam ring in response to a supply of the working oil into the first control oil chamber; a second control oil chamber configured to act a force in a direction in which the eccentricity quantity becomes large upon the cam ring in response to a supply of the working oil into the second control oil chamber; a switching mechanism formed to enable a switching between a state in which the working oil from the second control oil chamber is exhausted and a state in which the working oil is introduced into the second control oil chamber; and a control mechanism configured to take a state in which the working oil within the first control oil chamber is exhausted and another state in which the working oil whose pressure is decreased than a discharge pressure from the discharge section is introduced into the first control oil chamber and to perform a pressure regulation for the working oil while applying the pressure to the working oil within the first control oil chamber by introducing the working oil into the first control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the state in which the working oil is exhausted from the second control oil chamber, and to take a further another state in which the working oil whose pressure is decreased than the discharge pressure from the discharge section is introduced into the second control oil chamber and a still further another state in which an introduction of the working oil into the second control oil chamber via the switching mechanism is interrupted and the working oil within the second control oil chamber is exhausted and to perform the pressure regulation for the working oil while reducing the pressure to the working oil within the second control oil chamber by exhausting the working oil within the second control oil chamber as the discharge pressure becomes larger, in a case where the switching mechanism is in the other state in which the working oil is introduced into the second control oil chamber, wherein the control mechanism is controlled by a hydraulic pressure of the working oil and a biasing force of a biasing member and the working oil is not introduced into a location of the control mechanism at which the biasing member is arranged.
 18. The variable capacity oil pump as claimed in claim 17, wherein the first and second control oil chambers are disposed on an outer peripheral side of the cam ring and are defined by a swing fulcrum installed on the outer peripheral side of the cam ring. 